So, if you’re looking for tips on how to clean an air conditioner filter, keep reading our detailed guide below to get answers to all of your questions!
Why AC Units Make Loud Sounds When Starting
A normal, well-functioning air conditioner or heat pump should only make an almost indescribable low hum. If your air conditioner produces a ruckus every time it starts, there is very likely an issue with your air conditioner that needs to be addressed.
If you hear any banging, snapping, screeching, or clashing sounds every time your air conditioner turns on, you should give our HVAC professionals a call. One of our HVAC technicians can come out right away, diagnose, and fix your air conditioner or heat pump.
This guide introduces and explains the various noises an air conditioner can make while starting, how a professional will troubleshoot the noises, and how they are fixed.
Grinding, Squealing, and Screeching Noises
Harsh grinding and screeching noises coming from your AC system can come from your compressor or fan blower motor. If the grinding and screeching sounds are coming from the outdoor unit, the problem could be a variety of things:
- Broken or worn-out fan belt – a worn or a broken fan belt can make squealing and screeching noises and replacing the belt will solve this noise issue
- Bad fan motor bearings – the bearings in the blower wheel may lack lubrication and cause a screeching noise during startup but oiling the motor is a quick solution for this
- Motor failure – if the motor bearings go too long without oil, the noise can turn into a grinding noise and overwork the motor, causing it to fail
- The compressor is under high pressure – a high-pitched screeching noise from the outdoor unit is indicative of high pressure in your compressor and could potentially cause an explosion so if this is the case, turn it off and contact an HVAC technician immediately
- Compressor failure – loud grinding noises from the compressor can be caused by bad pistons within the compressor, which requires replacing the entire compressor to fix
Hissing or Whistling Sounds
Hissing and whistling sounds are almost always caused by leaking refrigerant. These sounds may only occur or just get louder when your air conditioner turns on. Leaking refrigerant can occur on the refrigerant lines, evaporator coils, condenser coils, or through the compressor valve.
Other, less common causes of whistling sounds are leaks in your ductwork, which can be fixed by sealing your ducts with, you guessed it – duct tape! Sealing ducts improves airflow, air quality, and overall system efficiency.
Unfortunately, there is no DIY solution to a refrigerant leak. Leaks need to be diagnosed and repaired by EPA-certified technicians. Thankfully, all of our HVAC technicians are EPA-certified to repair and recharge refrigerant so give us a call for help today!
Pulsating Noises
Light pulsation is common noise made by AC units and is perfectly normal. However, if the pulsation is very loud, especially when the air conditioner is starting, it’s an issue that needs to be addressed.
A loud pulsating noise that you can hear through the walls of your house can be caused by a loose fan blade, faulty fan motor, or other loose pieces within your AC fan. Pulsating sounds should be looked at and repaired by an HVAC technician.
Buzzing Sounds
Buzzing sounds are yet another odd noise that your air conditioner or heat pump could make while it is starting. Buzzing is usually caused by electrical problems that should only be diagnosed by a certified professional. You don’t want to shock yourself accidentally, so leave this sound to the AC repair pros to troubleshoot.
Buzzing can be caused by:
- Loose wires – exposed wires can spark, and arc electricity causes a buzzing noise
- Bad contactor – the contactor bridges the gap between the relay and the electricity supply; if it malfunctions, it can prevent the proper flow of electricity to the AC unit, causing a buzz
- Failing motor – motors that are failing often create a buzzing noise
- Failing capacitor – the capacitor energizes your compressor, and a failing one could make a distinct buzzing noise
- Broken compressor – similar to a failing motor, a broken compressor could generate buzzing sounds as well
Humming Noises
Humming noises are generally not something you need to worry about with your air conditioner. A running AC unit will have a slight hum during regular operation. However, if it is loud during start-up and is suddenly louder than before it is typically because of loose parts that are vibrating and create a hum.
Otherwise, humming during startup can come from the compressor if it has electrical issues such as a loose wire, a blown capacitor, or a bad relay. In both scenarios, excessive humming during start-up should be inspected by an HVAC expert.
Clamoring, Clanking, and Banging
Clamoring and loud banging noises when your air conditioning system is starting up are definitely not normal. It can also be loud enough to jolt you awake in the middle of the night.
Typically a loud clamor from your condenser unit is caused by dirt, and other debris stuck inside your outside unit. For example, if a stick falls perfectly through the outdoor unit, it could lodge against the compressor and bang against the condenser fins when it vibrates from the unit running.
There could also be loose parts like screws on your condensing unit that vibrate and cause a clanking noise when the compressor starts up.
Lastly, clamoring and loud banging noises can be caused by the fan motor or compressor going bad. These issues can also sound like a slamming noise at startup. If your compressor and outdoor fan motor are in good health, they should start and run with only a light hum.
Slamming noises can sometimes be caused by a damper or the ductwork reacting to a change in temperature. It can expand or contract, causing the sheet metal it’s made from to become convex or concave and pop.
If you hear any loud noises coming from the compressor, you should contact one of our HVAC specialists for help. Compressors typically have a lifetime warranty so don’t worry about a large repair bill!
Clicking and Rattling Noises On Startup
If you hear a few faint clicking noises when your AC system starts, that is generally nothing to worry about. However, if you hear constant, louder clicking or rattling noises at irregular intervals, it can signify electrical problems with your air conditioner.
Let’s go through the most common of these problems below.
Faulty Thermostat
A thermostat controls your air conditioning unit. It measures the indoor air temperature and tells the AC when to turn on and off.
If it fails, the relay switches inside it can start to make clicking noises, which signals that the internal relays are failing or there is an issue with the wiring. In either case, the thermostat needs to be serviced by an HVAC contractor.
Capacitor Failing
Failing capacitors can also cause clicking noises when the compressor unit is starting up. If the capacitor gets to the point of partial or complete failure, the clicking and rattling noise can become more apparent.
A failed capacitor requires complete replacement by a certified HVAC repair person.
Fan Obstruction
If there is an object, such as a twig, branch, or rock lodged in your outside unit, it could be perfectly placed to prevent your outdoor fan from engaging.
If the spinning can’t quite start because an obstruction is holding it back, you may hear a distinct clicking noise. Clearing the obstruction would solve the clicking sounds in this case.
The indoor fan could be obstructed by a dirty air filter. In that case, the startup noises can be resolved by cleaning or replacing the clogged air filter.
Loose Fan
Besides an obstruction, the fan can make clicking noises if it is loose as well. As the loose fan rotates, it can generate clicking noises as it wobbles.
The fan in your outdoor unit or air handler may be the culprit. Fixing the loose fan by tightening it screws of bolts fixes this issue.
Why Is It Important to Inspect Loud AC Sounds?
It is essential to inspect loud noises from your air conditioning system because it is usually a signal that something is wrong.
Ignoring the common causes of loud sounds when your AC unit is running or during regular operation can give the small issue time to transform into a catastrophic failure.
Refrigerant leaks and failures of critical components such as the blower or compressor can make your air conditioner completely inoperable. Don’t let your home’s AC stop running during the hot summer months – get your loud AC noises inspected right away!
When Should You Call An HVAC Specialist?
Most noises that an air conditioning system makes when starting cannot be DYI fixed by the homeowner. Instead, they need to be inspected and repaired by a certified HVAC professional.
We provide the best service and troubleshooting for all brands of HVAC systems and will ensure your system is running correctly and efficiently. Give us a call today to schedule your AC repair!
